The purpose of this project is to determine how and to what extent the perineurium is involved in the maintenance and regulation of the ionic and metabolic environment of the axons of peripheral nerves. The topics of interest included: (1) passive permeability to electrolytes and nonelectrolytes; (2) active transport of ions; (3) facilitated diffusion or transport of amino acids and glucose; (4) electrical impedance and short circuit currents; (5) the determination of normally existing composition of the extracellular fluid in the endoneurium.